The technology disclosed herein pertains to telecommunications, and particularly to structure and operation of a relay node in a cellular telecommunications system.
In a typical cellular radio system, wireless terminals communicate via a radio access network (RAN) to one or more core networks. Wireless terminals are also known as mobile stations and/or user equipment units (UEs). The wireless terminals can be mobile stations or user equipment units (UE) such as mobile telephones, “cellular” telephones, and laptops with wireless capability and/or mobile termination, and thus can be, for example, portable, pocket, hand-held, computer-included, or car-mounted mobile devices which communicate voice and/or data via the radio access network.
The radio access network (RAN) covers a geographical area which is divided into cell areas, with each cell area being served by a base station, e.g., a radio base station (RBS), which in some networks is also called “NodeB” or “B node”. A cell is a geographical area where radio coverage is provided by the radio base station equipment at a base station site. Each cell is identified by an identity within the local radio area, which is broadcast in the cell. The base stations communicate over the air interface operating on radio frequencies with the user equipment units (UE) within range of the base stations.
In some versions of the radio access network, particularly earlier versions, several base stations are typically connected to a radio network controller (RNC). The connection can be by landlines or microwave. The radio network controller, also sometimes termed a base station controller (BSC), supervises and coordinates various activities of the plural base stations connected thereto. The radio network controllers are typically connected to one or more core networks.
The Universal Mobile Telecommunications System (UMTS) is a third generation mobile communication system, which evolved from the Global System for Mobile Communications (GSM), and is intended to provide improved mobile communication services based on Wideband Code Division Multiple Access (WCDMA) access technology. UTRAN is essentially a radio access network using wideband code division multiple access for user equipment units (UEs). The Third Generation Partnership Project (3GPP) has undertaken to evolve further the UTRAN and GSM based radio access network technologies.
Long Term Evolution (LTE) is a variant of a 3GPP radio access technology wherein the radio base station nodes are connected directly to a core network rather than to radio network controller (RNC) nodes. In general, in LTE the functions of a radio network controller (RNC) node are performed by the radio base station nodes. As such, the radio access network (RAN) of an LTE system has an essentially “flat” architecture comprising radio base station nodes that do not report to radio network controller (RNC) nodes.
Relays have been identified as an important complement to boost system capacity of cellular communication systems based on standards like 3GPP LTE. A relay can be thought of as an enhanced repeater, where the cell coverage and also possibly cell-edge throughput can be extended/improved. A new interface, Un interface, exists between the traditional eNodeB and a relay node. An example of relaying in LTE-Advanced, also known as 3GPP Release 10, is Layer 3 relaying with self backhauling.
Various scenarios can be devised including everything from large outdoor relays operating very much like full-fledged base-stations serving large areas and many users to very small indoor relays for home or office use supporting very limited area and a few users. With a denser deployment of the latter the cost of relays has to be correspondingly lower till the point that the choice of radio architecture starts to have a major impact on total cost.
A simplified radio architecture may require the definition of new relay classes and associated functional and performance requirements in the standard. One such contribution is described in R1-101119, “Relay UL/DL timing discussion”, 3GPP TSG RAN WG1 Meeting #60, San Francisco, USA, 22-26 Feb. 2010, incorporated herein by reference in its entirety, where the aim is to reduce the number of transceivers by allowing transmission in one direction at a time, either on the Un link (UL frequency) or on the Uu link (DL frequency). Correspondingly, at any given point time reception is only allowed either on the Un link (DL frequency) or on the Uu link (UL frequency).